Two switch contacts 4 and 3 are soldered together along with the start wire of the coil. This leaves 3 wires: One switch wire goes to the battery positive the other to the positive electrode of the load in series with the ground. Along with it goes the end wire of the power coil, which connects to negative battery ground too.

When the button's depressed the SPDT switch closes and power runs from the positive of the battery through the coil and sends the magnet stack aloft. This frees the switch button and it returns to it's normally closed position after a very brief but significant delay, and shorts the power coil to the battery negative through the load. The attraction stroke is all gravy.